The history of mass assembly of faint red galaxies in 28 galaxy clusters since z = 1.3

Abstract

We measure the relative evolution of the number of bright and faint (as faint as 0.05L*) red galaxies in a sample of 28 clusters, out of which 16 are at 0.50 ≤ z ≤ 1.27, all observed through a pair of filters bracketing the 4000-A break rest frame. The abundance of red galaxies, relative to bright ones, is constant over all the studied redshift range, 0 < z < 1.3, and rules out a differential evolution between bright and faint red galaxies as large as claimed in some past works. Faint red galaxies are largely assembled and in place at z = 1.3 and their abundance does not depend on cluster mass, parametrized by velocity dispersion or X-ray luminosity. Our analysis, with respect to the previous one, samples a wider redshift range, minimizes systematics and put a more attention to statistical issues, keeping at the same time a large number of clusters.